A complete list of guidelines when diving with manta rays can be found at the Manta Pacific Research Foundation webpages, but to summarize:

only visual observation of manta rays is allowed when swimming with manta rays.

guest underwater swimmers must abide by your manta ray tour guide's requirements, one of which is that sufficient open water must be present between guest underwater swimmers and the manta rays to allow the mantas sufficient room to maneuver.

guest snorkelers must position themselves horizontally on the ocean's surface with sufficient open water present between themselves and the manta rays to allow the mantas sufficient room to maneuver.

guest swimmers and guest snorkelers with manta rays must follow their manta ray guides' instruction as to the direction that lights must be directed when around manta rays.

breathing must be timed so that guests do not allow bubbles to rise up into a manta ray if one were to pass overhead.

guest swimmers and guest snorkelers with manta rays must follow their manta ray guidelines when it comes to videotaping or photographing manta rays.

If you are interested in the manta ray identification project, please visit here for more information detailed at the Manta Pacific Research Foundation pages.